The present invention relates to air filter systems. In certain applications it concerns air filters for use in the air intake stream of gas turbine systems. In specific applications, it concerns filter constructions applied in gas turbine systems which are constructed to resist passage of moisture and/or salt therethrough. Methods of filtering to achieve such effect are also provided.
Although the present invention may be applied in a variety of applications, it was developed for use with gas turbine filter systems. Single stage, self cleaning air filter systems are known. One such system, commercially available, is the Donaldson GDX(trademark) Pulse Cleaning Filter System available from Donaldson Company, Inc., Minneapolis, Minn. In FIG. 1, a schematic, cross-sectional, depiction of a Donaldson GDX(trademark) Pulse Cleaning Filter System 20 is presented.
Referring to FIG. 1, the system 20 includes a chamber 21 having an air inlet side 22 and an air outlet side 23. Air enters the chamber 21 through a plurality of vertically spaced inlet hoods 26 positioned along the air inlet side 22. The inlet hoods 26 function to protect internal filters of the system 20 from the effects of rain, snow and sun. Also, the inlet hoods 26 are configured such that air entering the inlet hoods 26 is first directed in an upward direction indicated by arrow 27, and then deflected by deflector plates 28 in a downward direction indicated by arrow 29. The initial upward movement of air causes some particulate material and moisture from the air stream to settle or accumulate on lower regions 30 of the inlet hoods 26. The subsequent downward movement of air forces dust within the chamber 21 downward toward a dust collection hopper 32 located at the bottom of the chamber 21.
The chamber 21 of the system 20 is divided into upstream and downstream volumes 34 and 36 by a partition 38. The upstream volume 34 generally represents the xe2x80x9cdirty air sectionxe2x80x9d of the air cleaner system 20, while the downstream volume generally represents the xe2x80x9cclean air sectionxe2x80x9d of the system 20. The partition 38 defines a plurality of apertures 40 for allowing air to flow from the upstream volume 34 to the downstream volume 36. Each aperture 40 is covered by an air filter 42 or filter cartridge located in the upstream volume 34 of the chamber. The filters 42 are arranged and configured such that air flowing from the upstream volume 34 to the downstream volume 36 passes through the filters 42 prior to passing through the apertures 40.
For the particular filter arrangement shown, each air filter 42 includes a pair of filter elements. For example, each air filter 42 includes a cylindrical element 44 and, a somewhat truncated, conical, element 46. Each truncated, conical element 46 includes one end having a major diameter and another end having a minor diameter. The cylindrical element 44 and the truncated, conical element 46 of each filter 42 are co-axially aligned and connected end-to-end with the minor diameter end of each conical element 46 being secured to one of the cylindrical elements 44 in a sealed manner. The major diameter end of each truncated, conical element 46 is secured to the partition 38 such that an annular seal is formed around its corresponding aperture 40. Each filter 42 is generally co-axially aligned with respect to its corresponding aperture 40 and has a longitudinal axis that is generally horizontal.
In general, during filtering, air is directed from the upstream volume 34 radially through the air filters 42 into interior volumes 48 of the filters 42. After being filtered, the air flows from the interior volumes 48 through the partition 38, via apertures 40, into the downstream clean air volume 36. The clean air is then drawn out from the downstream volume 36, through apertures 50, into a gas turbine intake, not shown.
Each aperture 40 of the partition 38 includes a pulse jet air cleaner 52 mounted in the downstream volume 36. Periodically, the pulse jet air cleaner 52 is operated to direct a pulse jet of air backwardly through the associated air filter 42, i.e. from the interior volume 48 of the filter element outwardly to shake or otherwise dislodge particular material trapped in or on the filter media of the air filter 42. The pulse jet air cleaners 52 can be sequentially operated from the top to the bottom of the chamber 21 to eventually direct the dust particulate material blown from the filters into the lower hopper 32, for removal.
Arrangements such as those shown in FIG. 1 may be rather large. Filter pairs used in such arrangements commonly include cylindrical filters that are about 26 inches long and about 12.75 inches in diameter, and truncated conical filters that are about 26 inches long, about 12.75 inches in minor diameter, and about 17.5 inches in major diameter. Such arrangements might be used, for example, for filtering intake air to a gas turbine system having an air flow demand on the order of 8000 to 1.2 million cubic feet per minute (cfm).
A variety of types of filter elements have been used in arrangements such as that described above with respect to FIG. 1. Donaldson Company, Inc., for example, markets filter elements under the designation xe2x80x9cGDX filter elementsxe2x80x9d for such systems which comprise pleated paper having a web of submicron diameter fibers applied to a surface thereof, using proprietary, trade secret, Donaldson method, under the designation Spider-Web(copyright).
One aspect of the present invention relates methods and systems that use hydrophobic media to reduce the concentration or amount of water soluble material such as salt present in the intake air of a gas turbine engine or other type of environment that is sensitive to water soluble materials such as salt.
Another aspect of the present invention relates to a gas turbine intake air filter system including a first stage air cleaner for reducing the concentration of particulate material in the turbine intake air, and a second stage filter arrangement located downstream from the first stage air cleaner. The second stage filter arrangement includes a hydrophobic medium arranged and configured to reduce the concentration of moisture/salt solution in the intake air.
A further aspect of the present invention relates to a barrier arrangement for filtering water soluble material such as salt from an air stream such that the concentration of water soluble material is reduced. The barrier arrangement includes a plurality of vertically spaced-apart hydrophobic filter elements. The barrier arrangement also includes a plurality of inclined baffles arranged and configured to direct the air stream upward through the hydrophobic filter elements. Each of the baffles is positioned beneath a corresponding one of the hydrophobic filter elements. In operation, salt solution accumulates on lower surfaces of the filter elements. The accumulated salt solution drips from the filter elements onto the inclined baffles. The inclination of the baffles causes the salt solution to run downward and drip off upstream edges of the baffles.
An additional aspect of the present invention relates to a gas turbine system including a gas turbine adapted to draw intake air. The system also includes a hydrophobic medium through which the intake air is filtered prior to entering the gas turbine.
Still another aspect of the present invention relates to a method for filtering intake air of a gas turbine. The method includes the steps of filtering particulate material from the intake air at a first stage air cleaner, and directing the intake air downstream from the first stage air cleaner through an air flow gap to a second stage salt barrier. The method also includes the steps of reducing the concentration or level of salt in the intake air at the second stage salt barrier, and directing the intake air downstream from the second stage salt barrier to the gas turbine.
One further aspect of the present invention relates to a filter including a pleated filter element having a plurality of pleat tips, and an elastic member having portions that straddle the pleat tips and portions that extend between the pleat tips to maintain pleat spacing. In certain embodiments, the elastic member comprises a coil spring having a plurality of coils positioned between the pleat tips for maintaining pleat spacing of the pleated filter element.
A variety of advantages of the invention will be set forth in part in the description which follows, and in part will be apparent from the description, or may be learned by practicing the invention. It is to be understood that both the foregoing general description and the following detailed description are explanatory only and are not restrictive of the invention as claimed.